[router] Switch MCP tests from DeepWiki to self-hosted Brave search server

[key4ng]

Motivation

The MCP integration tests were using the external DeepWiki MCP server (https://mcp.deepwiki.com/mcp), which frequently hit rate limits during CI runs. This caused tests to be temporarily skipped, reducing test coverage for the MCP feature.

Modifications

Modifications

1. CI Infrastructure (.github/workflows/pr-test-rust.yml:262-271):
   - Added Dockerized Brave MCP server (shoofio/brave-search-mcp-sse:1.0.10) running on port 8001
   - Added health check and cleanup steps for container lifecycle management
2. Test Implementation (sgl-router/py_test/e2e_response_api/):
   - Replaced DeepWiki server URL with local Brave server (http://localhost:8001/sse)
   - Re-enabled previously skipped tests by removing @unittest.skip decorators
   - Refactored MCP test constants into shared class attributes for better maintainability
   - Updated test prompts to simpler queries about "sglang router news" with explicit result limits backends

Accuracy Tests

Benchmarking and Profiling

Checklist

• Format your code according to the Format code with pre-commit.
• Add unit tests according to the Run and add unit tests.
• Update documentation according to Write documentations.
• Provide accuracy and speed benchmark results according to Test the accuracy and Benchmark the speed.